1. Field of the Invention
The invention relates to a backlight module, and more particularly to a backlight module using line light sources.
2. Description of the Related Art
Recently, displays are to satisfy requirements for lower power consumption, slim style, high image quality, and no-radiation. Accordingly, the Thin Film Transistor Liquid Crystal Display (TFT-LCD) has become the main stream in the current market. The TFT-LCD is a non-active light-emitting display. The TFT-LCD mainly consists of a liquid crystal display panel, and a backlight module providing a stable lighting source.
The backlight modules can be designed to have a uniform surface light intensity using arrangement of light-emitting components and selection of optical materials. Typically, there are two types of backlight modules: an edge-lighting type and a direct-lighting type. The direct-lighting type backlight module can provide a surface source with higher brightness on a unit area, but it needs a light mixing space with a specific height, which is not conducive to slim-style design. According to the requirements, the edge-lighting backlight module is adopted to meet requirements for slim-style products.
Referring to FIG. 1, a conventional edge-lighting backlight module 1 is shown to include a light guiding plate 11, two light sources 12 disposed respectively on opposite lateral sides of the light guiding plate 11, and an optical element 13 disposed on the light guiding plate 11.
Light emitted by the light source 12, such as line light or point light, can be guided and mixed by the light guiding plate 11, and is then radiated out from a light exit surface 111 of the light guiding plate 11 in the form of surface light. The optical element 13 is disposed on the light exit surface 111 of the light guiding plate 11. Generally, the optical element 13 is a diffuser film to diffuse light and eliminate partly dark areas and further to converge and condense light so as to improve the light guiding effect of the conventional edge-lighting backlight module 1 when incorporating a brightening film.
When the conventional backlight module is applied to a large-size display panel, the following are some drawbacks of the conventional backlight module 1:                1. The light guiding plate 11 with a large size and high quality has a higher cost.        2. The large-size light guiding plate 11 easily deforms because of its heavy weight.        3. The large-size light guiding plate 11 easily becomes yellow and is deteriorated by environmental influences.        